The present invention relates to a data processing system which transfers data, and more particularly, to a data processing system which runs a plurality of operating systems (OS) thereon, and enables a channel device to simultaneously perform processing associated with the plurality of operating systems.
Conventionally, a main frame has supported an LPAR (Logical Partition) function for running a plurality of operating systems on one system under a control program.
In recent years, the LPAR function is supported not only by main frames but also by open servers. For supporting the LPAR function in an open server, a plurality of operating systems are required to share one channel device, because of a limitation in the number of slots which can be connected to channel devices involved in input/output processing. However, for a main frame which permits a plurality of operating systems to share a channel device as mentioned above, channel devices supported by the main frame tend to conform to specifications unique to the vendor of the main frame. Therefore, the sharing of a channel device by a plurality of operating systems is difficult for open servers which support channel devices conforming to the industry standard.
One of industry standard channel devices supported by open servers as mentioned above is Fibre Channel which has been developed by several vendors and conforms to a standard created by ANSI (American National Standards Institute). A protocol frequently used in Fiber Channel is FCP (Fibre Channel Protocol) which supports an SCSI (Small Computer System Interface) architecture. Since FCP does not define data in a frame for identifying an LPAR number or an operating system, difficulties are experienced in the sharing of a channel device by a plurality of operating systems. Also, for inserting a channel device, such as that conforming to Fibre Channel, into a slot of an open server for connection to a host processor in accordance with the industry standard, a PCI (Peripheral Component Interchange) bus, laid out by PCI-SIG, has been widely used in such a configuration. The PCI bus generally includes a PCI configuration register for one medium such as a channel device, and has only one control register for controlling the medium. Thus, for the foregoing reason, difficulties are also experienced in sharing a channel device by a plurality of operating systems.
In opposition to the industry standard channel device as described above, “FCP for the IBM eServer zSeries systems: Access to distributed storage” (IBM J. Res. & Dev. 46, No. 4/5 487-502) describes an exemplary channel device which can be shared by a plurality of operating systems. This channel device merely has one WWPN or Worldwide unique Port Name which is a channel device identifier associated with Fibre Channel, and appears as one port in a Fibre Channel network. While this limitation permits the channel device to be shared by a plurality of operating systems, only one operating system is allowed to access one Fibre Channel device identified by LUN (Logical Unit Number) at a certain arbitrary time. Also, the channel device is not inserted into a slot of the PCI bus, but into a bus slot of a server, which conforms to the specifications unique to the vendor of the server.
Further, in recent years, port multiplexing has been developed for connecting a plurality of ports to a single slot in order to effectively utilize slots of a server. However, the aforementioned prior art technique is not directed to a channel device which implements the port multiplexing.